This invention relates to field of data recording and retrieval. More particularly, it relates to apparatus for "write protecting" data storage disks (e.g. optical, magneto-optical and magnetic disks) to prevent inadvertent data overwrite or erasure.
In the commonly assigned U.S. application Ser. No. 923,508, filed on Oct. 27, 1986 in the names of Dwight J. Petruchik et al., there is disclosed an optical disk assembly comprising a rectangular frame known as a "carrier" which is adapted to releasably support and retain a rigid optical disk. The carrier and its associated disk are enclosed by a box-like enclosure, known as a "caddy," which serves to protect the relatively delicate recording surfaces of the optical disk during periods of non-use. When inserted into the clean environment of a suitable disk drive unit, the carrier and its associated disk are extracted from the caddy, and the latter is returned to the user. Thereafter, the disk is released from its supporting carrier and lowered onto a spindle/turntable for rotation. Following use of the disk within the disk drive unit, the disk is returned to its carrier (which remains within the disk drive unit while the disk is being used). Thereafter, a caddy, possibly a different caddy, is reinserted into the drive unit to receive the carrier/disk assembly. After reloading the carrier/disk assembly into the caddy, the disk drive unit returns the caddy/carrier/disk package to the user.
In virtually all data storage disk assemblies, it is desirable to provide a "write-protect" feature, that is, some mechanism for preventing inadvertent overwrite and, hence, erasure of information already recorded on the disk. Such feature often takes the form of an aperture or notch formed in the disk's protective sleeve or carrier, such feature being adapted to cooperate with a sensor of some sort within the disk drive to produce a write-protect signal that can be used to either inhibit or enable writing on the disk. In optical disk assemblies, it is essential to maintain the recording surfaces of the disk substantially free of any and all contaminants; thus, in disk assemblies of the type mentioned above, it would be desirable to control the write-protect feature on the carrier from outside the caddy which encloses the carrier. This would allow the write-protect status of the disk to be changed without violating the clean-air integrity of the caddy. Also, it is desirable that the write-protect status indicator on the caddy always reflect the write-protect status of the disk/carrier contained thereby. Since it is possible, as noted above, that a disk/carrier can be reloaded, following use in a disk drive unit, into a different caddy from that which had previously contained the disk, a write-protect indicator (if any) on the caddy may, at the time of reloading, falsely reflect the write-protect status of the disk/carrier which is being reloaded into the caddy.